摘要:

This is the first report of an extrafloral nectary in the Punicaceae. Each leaf of pomegranate bears a single apical nectary that consists of a closely packed spherical mass of densely staining cells, and of a surrounding layer of cells that are larger and more vacuolate, though still densely staining. The epidermis at the apex of the nectary (which is also comprised of small, densely staining cells) bulges to form a bump over a small chamber. The leaf apex lacks stomata or other specialized pores for nectar to escape. However, separation of epidermal cells and conspicuous ruptures sometimes occur. The midvein and 2–4 lateral bundles converge on the nectary. The xylem stops before reaching the nectary, but the phloem continues, curving about halfway around the nectariferous tissue. Chromatographic analysis of nectar droplets showed roughly equal amounts of fructose, glucose, and sucrose. This nectary resembles leaf apical glands ofLafoensiain the closely related family Lythraceae.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb07875.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

An evaluation of possible approaches to fossil oak pollen identification utilized scanning electron microscopy to examine exine‐surface features of 171 collections, representing 16QuercussubgenusLepidobalanusspecies and varieties of eastern North America. Twenty qualitative pollen morphological characters were defined and tabulated for each of 217 pollen grains. The data were subjected to cluster analysis and cluster diagrams were compared with published white oak taxonomy. Pollen morphology and plant taxonomy compared well in series of the subgenusLepidobalanusdue primarily to consistency of character presence and absence within species and varieties. Pollen morphology of white oaks appears to reflect plant systematics above the species level. Use of routine SEM analysis to identify series of white oaks among fossil pollen grains likely will yield valid results.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb07876.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Identification ofQuercus(oak) pollen taxa could enhance Quaternary palynological interpretations from eastern North America. A first step is to determine a morphological and taxonomic basis for such identifications. Scanning electron microscopy was utilized to examine exine‐surface features of 266 specimens representing 21 red oak (subgen.Erythrobalanus) species from eastern North America, and two intermediate oak (subgen.Protobalanus) species from the desert southwest. Twenty pollen morphological characteristics defined previously were tabulated for each of 324 pollen grains. The data were subjected to cluster analyses. Cluster diagrams were compared with traditional oak systematics. Pollen morphology and plant taxonomy compared poorly with respect to series and species relationships among the red oaks, apparently due as much to high intraspecific and low interspecific variability in pollen‐morphological characters as to the uncertain taxonomy of red oaks. Pollen morphology, however, does support the hypothesis of subgeneric oak evolution from intermediate oaks to the seriesVirentesof white oaks, and from more advanced white oaks to the red oak species.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb07877.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

The paired flowers of all species of the Marantaceae studied, exceptMonotagma plurispicatum, are produced through the division of an apical meristem with a tunica‐corpus structure. The solitary flowers ofM. plurispicatumdevelop from a similar meristem which does not bifurcate. The paired flowers ofCanna indicaare produced in the axil of a florescence bract through the formation of a bract and an axillary flower on the side of the primordium which gives rise to the largest flower of the pair. The sequence of organ initiation for both families is: calyx, corolla and inner androecial whorl, outer androecial whorl, gynoecium. The sequence of sepal formation is opposite in the two families. In the Cannaceae it leads directly into the spiral created by the formation of the other organs, while in the Marantaceae the sequence of sepal formation follows a spiral opposite to that of the other floral organs. The members of the corolla and inner androecial whorl separate from common primordia. In general these common primordia separate into a petal and an inner androecial member through the initiation of two growth centers, at the same level, in the dorsal and ventral flanks of the primordium. InIschnosiphon elegansandPleiostachya pruinosathe stamen is initiated at a lower position than the petal in the ventral flank of the common primordium. A similar pattern of initiation is described for the callose staminode inMarantochloa purpureaandCanna indica. This pattern is interpreted as a variation on the more generalized pattern of inner androecial formation found in the other genera.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb07878.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Morphogenesis of calluses of single pollen grain origin shed from anthers ofHyoscyamus nigercultured in a liquid medium containing 2,4‐dichlorophenoxyacetic acid (2,4‐D) was followed upon their transfer to a solid medium with or without 2,4‐D. In a solid medium lacking 2,4‐D, small calluses consisting of one to five nodular groups of cells at the time of inoculation differentiated root and shoot systems and formed miniature seedlings. In the same medium large calluses with several nodules initially formed a crop of bipolar somatic embryoids with well‐defined root and shoot axes which subsequently differentiated into seedlings. Irrespective of their size at the time of transfer, calluses grown in a solid medium containing 2,4‐D continued to proliferate without showing signs of organogenesis or embryogenesis.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb07879.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Endogenous adventitious buds develop in situ from dedifferentiated parenchyma cells of the trunk‐bark in the temperate treesTilia platyphyllos, Acer pseudoplatanus, andFraxinus excelsior, as well as in the tropical cauliflorous treesArtocarpus integrifolia, Swartzia schomburgkii, andCouroupita guianensis. On aerial roots ofClusia roseaendogenous adventitious buds originate within the proliferated phelloderm beneath lenticels. InSalix alba, Fraxinus excelsior, andTerminalia arjuna, exogenous dormant buds are overgrown during secondary growth and engulfed within the bark tissue, so that they give the impression of apparent endogeny. In the leaf axils of young shoots ofAraucaria angustifolia, superficial tissue layers divide and form axillary protrusions, which soon become parenchymatic and partly suberized. A few cells at their bases stay meristematic, however, and develop as rudimentary endogenous bud primordia, which persist in the bark for many years.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb07880.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Analyses of the ultrastructural states of preservation seen in fossil angiosperm mesophyll cells indicate that plastids are more commonly found in portions of protoplasts (= microprotoplasts) lacking nuclei than in microprotoplasts containing nuclei. Of the 4,498 cells examined in serial thick sections, less than 1.8% had continuous protoplasts, while the remaining 98.2% had from 2 to 3 microprotoplasts or lacked any discernable internal structure. Where nuclei and plastids were found in the same cell (21.3%), only 29.5% had these two organelles in the same microprotoplast, while 70.5% had nucleate microprotoplasts lacking plastids and enucleate microprotoplasts with well preserved plastids. Over 64% of all the cells sampled lacked nuclei but had well preserved plastids.Neobotanical studies indicate nuclei are more stable than plastids, but during microprotoplast formation plastids are more stable in enucleate protoplasts than in those containing nuclei. Senescence and necrosis are triggered by the nuclear genome. The preferential preservation of plastids in fossil angiosperm tissues is interpreted to be the result of the isolation of part of the plastid population from nuclear control due to microprotoplast formation. This hypothesis also may explain the apparent longevity of nuclei over plastids in other fossil cells (spores, pollen, algal tissues) where protoplasmic partitioning may be less frequent.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb07881.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Artificial hybridization, fertility of interspecific and intersectional hybrids, chromosome numbers, and trends in habit and morphology in taxa of sectionsEublepharisandCalliopsisof the genusCoreopsisare used to consider the sectional relationships and to derive a presumed phylogeny for the two sections. The two sections are closely related and show a low level of interfertility, but this level is as high as in some interspecific crosses within sections. The sections differ in base chromosome number and achene winging. The problematicC. roseaevidently should remain in sectionEublepharis. Both sections probably arose fromx =13 stock resembling C.integrifoliaorC. pubescens. Descending aneuploidy was involved in the derivation of sectionCalliopsis, while chromosome evolution in sectionEublepharishas involved polyploidy.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb07882.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

The placental ridge began to proliferate 10 days after pollination. Megaspore mother cell underwent meiosis to form two dyads at first division. At 50 days two megaspores and generating dyad were formed by second division. The functional megaspore divided successively three times to form an eight‐nucleate embryo sac at 60 days. Double fertilization occurred forming the zygote and endosperm initial cell. However, the endosperm initial cell degenerate soon thereafter. The zygote divided to form a terminal cell, the middle cell and suspensor initial cell at 70 days. The terminal and middle cells successively divided to form a multi‐celled embryo up to 120 days after pollination. Histochemical study showed that the stainability of DNA, RNA and total proteins were almost constant during ovule and embryo development. Stainability of total carbohydrates decreased.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb07883.x

出版商:Wiley    

年代:1983

数据来源: WILEY

摘要:

Water‐use characteristics and potential salt accumulation rates were studied in three halophytes,Salicornia virginica, Balis marítimaandBorrichia frutescens, inhabiting a salinity gradient in the high marsh. Xylem pressure potential (ψρ), leaf osmotic potential (ψπ) and leaf relative water content were measured seasonally in the three species. Species growing on the high end of the salinity gradient developed more negative xylem pressure potentials compared to species growing at lower soil salinities. This trend was also observed for leaf osmotic potentials. Low mean leafψπ(below –15 to –36 bars) and high ash contents (0.27–0.48 g NaCl/g DW) indicated salt accumulation in transpiring tissues. However, calculations of potential salt accumulation, based on rates of transpiration and substrate salinity, suggest that some mechanism of salt exclusion at the roots may be operating.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1983.tb07884.x

出版商:Wiley    

年代:1983

数据来源: WILEY